Compressor



July 28, 1942. c w, R 2,290,858

COMPRESSOR Filed Jan. 31, 1940 .2 Shee ts-Sheet 1 24; A MM- I V y 1942-c. w. BROWN COMPRESSOR Filed Jan. 51, 1940 2 Sheets-Sheet 2 66627 2%32mm 2g AwM'H/mxm,

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Patented July 28,1942

UNITED v COMPRESSOR Cecil w. Brown, Elm Grove, was;

as'algnor to Sullivan Machinery Company, a corporation of MassachusettsApplication January 31, 1940, Serial No. 315,568

12 @Claims.

My invention relates to compressors, and more particularly to devicesfor automatically controlling the unloading of a compressor inaccordance with discharge pressure.

It is an object of my invention to provide an improved device forefiecting step-by-step unloading of a compressor. It is another objectof my invention to provide an improved compressor discharge pressurecontrolled and actuated unloading system for a compressor adapted toefiect step-by-step unloading of the latter. It is still another objectof the invention to provide an improved pilot mechanism adapted forcompressor control. It is yet a further object of my invention toprovide an improved device for automatically controlling thestep-by-step unloading of a compressor and having adjustable means operative to eflect its responsiveness to the pressures to be controlled,whereby changes may readily bemade to suit difierent conditions. Otherobjects and advantages of my invention will hereinafter more fullyappear.

In the accompanying drawings, in which I have shown one form which theinvention may assume in practice.

Fi 1 is a diagrammatic view, partly in vertical section, showing theinvention applied in a single cylinder compressor so as to effecttour-step unloading of the latter.

Fig. 2 is a view oi the fluid pump taken on the plane of the line 2-4 ofFig. l with a portion oi the casing broken away.

Fig. 3 is an enlarged horizontal sectional view, looking up, through theautomatic device ior controlling the flow of pressure fluid to thecompressor unloading elements, taken on the plane of the line 3-3 01Fig. l.

Fig. 4 is a vertical sectional view through the unloading controldevice, taken on the line 6-4 of Fig. 3. 1

It will be evident that my invention from its control aspect may beutilized with single or multiple compressor cylinders and with single ormultiple stage compressors To illustrate a preferred embodiment of theinvention there is shown a compressor cylinder l having a bore 2 closedat its ends by cylinder heads 3 and in which a piston 4 reciprocates.Air is supplied to the cylinder bore from an intake connection 5 througha chamber 6 and inlet valves 1 at the head and crank ends of thecylinder. Discharge valve mechanisms 8 are provided at the head andcrank ends oi the cylinder, through which com-.- pressed air isdischarged to a chamber 9 in the cylinder, and through a dischargeconnection I0 to a receiver H.

Suitable inlet valve opening devices are provided, and are shown here ascomprising pistons 93 carrying fingers I4 and operating in cylindersiii. The fingers are normally held in a retracted position by springs IEbut are moved to unseat the inlet valves when pressure fluid is suppliedto the cylinders Ii through pipes H and 18. Clearance chambers I9 areprovided in the compressor cylinder, having communication with the headand crank ends of the cylinder bore through passages 20. Clearancevalves 26 are provided in the clearance chambers, and each valve has apiston 22 operating in a cylinder 23. Springs 24 normally maintain theclearance valves in position to shut ofi communication between theclearance chambers and cylinder bore through passages 28. The clearancevalves are opened when pressure fluid is conducted to the lower surfacesof the pistons by pipes 25 and 26. It will be appreciated that theunloading devices for the compressors or cylinders (it a plurality ofcylinders are employed) may be of various kinds and that the number orsteps of unloading may be varied at the will of the designer,

In my invention I have provided improved means for partially or totallyunloading and for reloading the compressor cylinder described above infour steps automatically as the pressure in the receiver varies. Forthis purpose I use a pilot valve mechanism, generally designated 21,which is adapted to connect the receiver through a pipe 28, if desiredwith the interposition of a valve of the type which transmits only thepressures in excess of any selected value, to the inlet valve openingdevices through pipes H and I8, and to the cylinders 23 through thepipes 25 and 26 for opening the clearance valves 2 I The pilot valvemechanism comprises, as shown in Figs. 3 and 4, a block 29 having acentral bore 30 extending through it, and bores 3|, having equaldiameters,

formed within the block 29 surrounding the central bore 30. The bores 3|severally open into larger bores 32, 33, 34 and 35, each having adifferent. cross sectional area and each opening through the lowersurface of the block. Reciprocably mounted in the bores surrounding thecentral bore are pistons severally designated 36, 38 36" and 36 andeachhaving a portion fitting the bores 3| and respectively havingportions fitting the larger bores 32, 33, 34 and 35. Pipes l1, I8, 25and 28 communicate with the bores 33, 35, I2 and 34 respectively throughpassages 31, 38 3! and in the block 29 at points overrun by the lowerends of plungers or pistons 36, 36, 36 and 36 when in their raisedpositions and below whichthe tops of the enlarged piston portions passwhen in their lower positions. Vent passages 4| connect'the upper endsof the bores 32,

- to a value sufiicient to force the piston 36',

and formed in the block 26. A pipe 48 connects the central bore 30 to afluid pump 49, The fluid pump may be of any suitable constant pressuretype, and is shown here as comprising a casing 50 enclosing a fluidreservoir 5| and meshing pinions 52 and 53, one of which is fixed on ashaft 54 mounted in a suitable bearing 55 attached to the pump casing,while the other pinion is rotatable on a stud 55' carried by the pumpcasing. Any suitable means may be attached to the shaft 54 for drivingthe pinions 52 and 53. A passage 56 in the pump casing connects the pipe48 to a point adjacent the pinions 52, 53. A passage 51 in the pumpcasing is adapted to connect the passage 56 to the reservoir 5|, and arelief valve 58 having a guide element 53 operating in a cylinder 60 isnormally pressed by a spring 6| to close oil communication between thereservoir 5| and passage 51. The compression of the spring is adjustedby a threaded cap 62. Attached in fluid-tight relationship to the block29 at one end of the central bore 3|] is a flexible diaphragm or bellowselement 63 carrying a plate 64 at its upper end. An arm 65 carrying aslidably adjustable weight 66 at one end is pivoted at its other end 61to a support 68 attached to the block 29. The arm presses against theplate 64 attached to the upper end of the flexible diaphragm 63.

The mode of operation is as follows:

The fluid pump 49 is started to pump fluid from the reservoir 5| throughthe pipe 43 to the central bore 36. As a pressure builds up in the bore3|) the flexible diaphragm 63 expands, lifting the arm 65 and weight 66.When the pressure attains a value suflicient to; lift the relief valve53 against the pressure of the spring 5|, fluid will be pumped throughthe passage 57 back into the reservoir. By adjusting the weight 66 onthe arm 65 and the compression of the spring 6| by the threaded cap 62,any desired constant pressure may be maintained in the central bore 30.The fluid under pressure will be conducted from the bore 30 through theradial passages 41 to the bores 3|, where it will act against-the upperends of the pistons 36', 36 36 and 36 and continuously urge them towardtheir lower positions.

Pressure fluid is conducted from the receiver through pipe 28 to thechamber and flows through passages 46 to the cylinder bores 32, 33, 34and 35, where it acts on the lower ends oi. the pistons 36, 36", 36 and36 and urges them toward their raised position Assuming that thepressure in the chamber 45 is insufllcient to raise any of the pistonsagainst the pressure in the bores 3|, the pipes l1, I3, 25 and 26 willbe vented through the bores 33, 35, 32 and 34, and vent passages 4|; theinlet valve opening devices will be retracted by the springs I6 topermit the inlet valves to operate in their normalmanner, and theclearance valves will be held closed by springs 24. The compressorcylinder the'n operates iully having its lower end fitting the largebore 32, to its upper position. Pressure fluid then flows from thereceiver through pipe 2'3, chamber 45, passage 46, bore 32 and pipe 25to open the clearance valve 2| at the head end of the compressorcylinder against the spring, 24. The compressor cylinder then operatesat three-quarters load, and it the demand for air is low and thereceiver pressure continues to increase, it will, at a higher pressure,move the piston '36 having its large end fitting the bore 33, to itsupper position. Pressure fluid will then flow from the chamber 45through bore 33 and pipe I! to the cylinder l5, where it moves thefingers to open the inlet valve at the head end of the cylinder andcompletely unload that end of the cylinder. If the receiver pressurestill continues to increase, it will ultimately move the piston 36having its large end fitting the bore 34, to its upper position andpressure fluid will flow from chamber 45 through the bore 34 and pipe 26to open the clearance valve in the crank end of the compressor cylinder.The compressor cylinder then operates threequarters unloaded, and it thereceiver pressure increases to a value sufficient to move the piston 36,having its large end fitting the bore 35, to its upper position,pressure fluid will flow from the chamber 45 through bore 35 and pipe l3to open the inlet valve in the crank end of the compressor cylinder andcompletely unload the cylinder.

If the demand for air increases and the receiver pressure drops, thepressure acting on the upper ends oi. the pistons 36, 36, 36 and 36'?will move them to their lower positions in an order reverse to that ofunloading, and vent the pipes I6, 26, I! and 25 through bores 35, 34, 33and 32, and vent passages 4|, thereby permitting the inlet valves tooperate in their normal manner and the clearance valves to close,reloading the compressor insteps.

It will be appreciated that the expansible bellows will enable theseveral plungers to move upwardly without the amount or retardation thatwould be present it the fluid displaced had all to be pushed throughthepassage 51 in order for the plungers to move. It will be understood,moreover, that the pressure diflerentials may be made quite small, andby suitably proportioning and selecting the areas wide ranges ofpressures may easily be provided for with minor changes in design. Thedevice is strong and simple and does not depend on small pressure areasor passages for operativeness.

While I have in this application specifically described one form whichmy invention may assume in practice, it will be understood that thisiorm is shown for purposes of illustration and that the invention may bemodified and embodied in various other forms without departing from itsspirit or the scope of the appended claims.

What I claim as new and desire to secure by Letters Patent is:

1. In a control device, a cylinder block, a pmrality oi bores in saidcylinder block each having the same diameter, a plurality oi'bores insaid cylinder block having diflerent diameters and each opening into adifferent one of said first mentioned plurality of bores, pistonsreciprocable in said bores and having heads fitting the bores openinginto each other, means for subjecting said pistons at one end to aconstant pressure, and

. rocable in said bores and plurality of bores in the same diameter, aplurality of bores in saidir,

cylinder block having diflerent diameters and each in axial alinementwith and opening into a diflerent one or said first mentioned pluralityof bores, pistons reciprocable in said bores and having heads fittingthe bores opening into each other, means for subjecting the ends of saidpistons fitting the bores having the same diameter to a constantpressure, and means for subjecting the opposite ends of said pistons toa pressure to be controlled.

3. In a control device, a cylinder block, a pressure chamber in saidcylinder block, a plurality of bores in said cylinder block eachhavingthe same diameter, passage means connecting said pressure chamber withsaid plurality of bores, a plurality of bores in said cylinder block iorsubjecting the larger ends of said plungers to a pressure .to becontrolled, means for subjecting the smaller ends or said plungers to arelatively constant pressure and adapted to maintain substantialunitormity of pressure regardless of plunger movements, and fluiddelivery and exhaust lines communicating with each or v the largerbores.

having difierent diameters and each in axialalinement with and openinginto a different one of said first mentioned pluraiity of bores, pistonsreciprocable in said bores and having heads fitting the bores openingsubjecting the ends of said pistons fitting the bores having difierentdiameters to a pressure to be controlled, and means for creating in saidpressure chamber a constant control pressure.

4. In acon trol sure chamber in said cylinder block, a plurality ofbores in said cylinder block each having the same diameter, passagemeans connecting said pressure chamber with plurality of bores in saidcylinder block having diilerent diameters and each in axial alinementwith and opening into a difierent one 0! said first mentioned pluralityof bores, pistons reciphaving. heads fitting the bores opening into eachother, means for subjecting the ends or said pistons fitting the boreshaving diflerent diameters to a pressure to be controlled, means forsupplying pressure fluid to said pressure chamber, and means forcontrolling the pressure in said chamber including an expansible elementattached in fluid-tight relationship to one end of said chamber.

5. In a control device, a cylinder block, a pressure chamber in saidcylinder block, a plurality of bores in said cylinder block each havingthe same diameter, passage means connecting said pressure chamber withsaid plurality of bores, a said cylinder block having diiferentdiameters and each in axial alinement with and opening into a cable insaid bores and having heads fitting the bores opening into each other,means for subjecting the ends of said pistons fitting the bores havingdifferent diameters to a pressure to be controlled, means for supplyingpressure fluid to said pressure chamber, and means for controlling thepressure in said chamber including an expansible element attached influid-tight relationship to one end of said chamber and adjustable meansfor opposing the expansion or said expansibleelement.

6. In combination, in a controlling apparatus.

into each other, means for said plurality of bores, a

device, a cylinder block, a pres- 7. In a valve device for controllingthe distribution of a pressure fluid, in combination, a plurality ofmovable valve members having oppositely directed unequal pressure areas,means supporting said valve members for movement relative to each other,a pressure chamber, means for creating in said pressure chamber aconstant control pressure, means tor subjecting the pressure areas onsaid valve members directed in one direction to the pressure in saidpressure chamber, means for supplying pressure fluid to the pressureareas on said valve members that are directed oppositely from the areassubjected to the pressure in said pressure chamber, and fluid deliverylines communicable with said pressure fluid supply means onpredetermined move-- ment of said valve members.

8. In a valve device for controlling the distribution of a pressurefluid, in combination, a

plurality of movable valve members having oppositely directed pressureareas, the pressure areas directed in one direction being equal to eachother and those directed in the opposite direction being difierent fromeach other, means supporting said valve members for movement relative toeach other, a pressure chamber, means for creating in said pressurechamber a constant pressure,'means for subjecting the equal pressureareas on said valve members to the pressure in said chamber, means forsupplying pressure fluid to the pressure areas on said valve membersthat are different from each other, and fluid delivery linescommunicable with said pressure fluid supply means on predeterminedmovedifierent one of said flrst I mentioned plurality of bores, pistonsrecipro-,

means forming a plurality of differential bores,

of which the smaller portions are of like cross sectional area and thelarger portions-oi difierent cross sectional area, plungers in each ofsaid difierential bores each having a portion fltting each portion ofits respective differential bore, means ment of said valve members.

9. In a valve device for controlling the distribution of a pressurefluid, in combination, a plurality of movable valve members havingunequal pressure areas, means supporting said valve members for movementrelative to each other, means for subjecting said valve members to aconstant force opposing movement of said members in one direction, meansfor supplying pressure fluid to the unequal pressure areas on said valvemembers, and fluid delivery lines communicable with said pressure fluidsupply means on predetermined movement 0! said valve members.

10. In a device for controlling the distribution of a fluid underpressure to a pressure responsive control mechanism, a plurality ofmovable valve members each having oppositely directed imequal pressureareas, means for subjecting the pressure areas directed in one directionto a constant pressure, means for subjecting the pressure areas directedin the opposite direction to a pressure to be controlled, and meansoperative on predetermined movement of said valve members in oppositionto said constant pressure for supplying pressure fluid to the pressureresponsive control mechanism.

- 11. In a device for controlling the distribution to a constantpressure, means for subjecting the pressure areas. directed in theopposite direction to a, pressure to be controlled, and means forsupplying pressure fluid to said controi mechanism and for ventingpressure fluid from said control mechanism, said supply and ventingmeans including passage means controlled by said valve members.

12. In a device for controlling the distribution of a. fluid underpressure to a pressure responsive control mechanism, e cyiinder block, aplurality of bores formed in said cylinder block and each having it esame diameter, a plurality of bores oi difierent diameters iormezi insold cylinder block and each in exile-J. eiinement with and opening intoa difierent one of said first mentioned plurality oi bores, pistonsrciprocable in said bores and having heads fitting the bores openinginto CECIL W. BROWN.

